AJP - Gastrointestinal and Liver Physiology

Gillingham, Melanie B.; Dahly, Elizabeth M.; Carey, Hannah V.; Clark, Melanee D.; Kritsch, Karen R.; Ney, Denise M.

doi: N/Apmid: 10801262

Abstract Patients with severe short-bowel syndrome (SBS) often require long-term total parenteral nutrition (TPN) to maintain their nutritional status because of limited intestinal adaptation. Growth factors, including insulin-like growth factor I (IGF-I), are under investigation to promote intestinal adaptation and tolerance to oral feeding. We investigated structural and functional adaptation of the jejunum and colon in four groups of rats maintained with TPN for 7 days after a 60% jejunoileal resection and cecectomy or sham surgery and treatment with IGF-I or vehicle. Resection alone did not stimulate jejunal growth. IGF-I significantly increased jejunal mucosal mass, enterocyte proliferation, and migration rates. IGF-I decreased jejunal sucrase specific activity and reduced active ion transport and ionic permeability; resection alone had no effect. In contrast, resection significantly increased colonic mass and crypt depth but had no effect on active ion transport or ionic permeability. IGF-I had minimal effects on colonic structure. IGF-I but not resection stimulates jejunal adaptation, whereas resection but not IGF-I stimulates colonic growth in rats subjected to a model for human SBS. IGF-I treatment may improve intestinal adaptation in humans with SBS. 60% jejunoileal resection cecectomy gut adaptation short-bowel syndrome ion transport Footnotes Address for reprint requests and other correspondence: D. Ney, Dept. of Nutritional Sciences, Univ. of Wisconsin, 1415 Linden Dr., Madison, WI 53706 (E-mail: [email protected] ). This study was supported by National Institute of Diabetes and Digestive and Kidney Diseases Grants RO1-DK-42835 and T32-DK-07665 and funds from the College of Agriculture and Life Sciences, University of Wisconsin. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 2000 the American Physiological Society

Kawachi, Shigeyuki; Jennings, Stephen; Panes, Julian; Cockrell, Adam; Laroux, F. Stephen; Gray, Laura; Perry, Michael; van der Heyde, Henry; Balish, Edward; Granger, D. Neil; Specian, Robert A.; Grisham, Matthew B.

doi: N/Apmid: 10801266

Abstract The objectives of this study were to quantify cytokine mRNA levels and endothelial cell adhesion molecule message and protein expression in healthy wild-type and interleukin-10-deficient (IL-10 −/− ) mice that develop spontaneous and chronic colitis. We found that colonic message levels of IL-1, IL-6, tumor necrosis factor-α, interferon-γ, lymphotoxin-β, and transforming growth factor-β were elevated in colitic mice 10- to 35-fold compared with their healthy wild-type controls. In addition, colonic message levels of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) were found to be increased 10-, 5-, and 23-fold, respectively, in colitic IL-10 −/− mice compared with their wild-type controls. Immunoradiolabeling as well as immunohistochemistry revealed large and significant increases in vascular surface expression of colonic ICAM-1, VCAM-1, and MAdCAM-1 in the mucosa as well as the submucosa of the colons of colitic mice. These data are consistent with the hypothesis that deletion of IL-10 results in the sustained production of proinflammatory cytokines, leading to the upregulation of adhesion molecules and infiltration of mononuclear and polymorphonuclear leukocytes into the cecal and colonic interstitium. leukocytes inflammation immunology Footnotes Address for reprint requests and other correspondence: M. B. Grisham, Dept. of Molecular and Cellular Physiology, Louisiana State Univ. Medical Center, P.O. Box 33932, Shreveport, LA, 71130 (E-mail: [email protected] ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 2000 the American Physiological Society

Turner, Jerrold R.; Liu, Lei; Fligiel, Suzanne E. G.; Jaszewski, Richard; Majumdar, Adhip P. N.

doi: N/Apmid: 10801273

Abstract Administration of pharmacological doses of epidermal growth factor (EGF) or transforming growth factor-α (TGF-α) in young rats stimulates gastric mucosal proliferation, but, in aged rats, the same treatment inhibits proliferation. This may be due to enhanced ligand-induced internalization of EGF receptor (EGFR). In support of this, we demonstrated that although a single injection of EGF (10 μg/kg) or TGF-α (5 μg/kg) in young (4–6 mo old) rats greatly increased membrane-associated EGFR tyrosine kinase activity, the same treatment slightly inhibited the enzyme activity in aged (24 mo old) rats. This treatment also produced a greater abundance of punctate cytoplasmic EGFR staining in gastric epithelium of aged rats, consistent with EGFR internalization. In vitro analyses demonstrated that exposure of isolated gastric mucosal cells from aged but not young rats to 100 pM TGF-α resulted in marked increases in intracellular EGFR tyrosine kinase activity and that induction of EGFR tyrosine kinase activity in mucosal membranes from aged rats occurred at doses 1,000-fold less than those required in young rats. Our data suggest that aging enhances sensitivity of the gastric mucosa to EGFR ligands. This may partly explain EGFR-mediated inhibition of gastric mucosal proliferation in aged rats. epidermal growth factor receptor epidermal growth factor receptor internalization cell proliferation tyrosine kinase Footnotes Address for reprint requests and other correspondence: A. P. N. Majumdar, Research Service-151, Veterans Affairs Medical Center, 4646 John R, Detroit, MI 48201 (E-mail: [email protected] ). This study was supported by the National Institute on Aging and the Department of Veterans Affairs (A. P. N. Majumdar) and National Institute of Diabetes, Digestive, and Kidney Diseases Grants DK-02503 and DK-56121 (J. R. Turner) and Institute of Chemical Toxicology of Wayne State University Grant NIH P30-ES06639. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 2000 the American Physiological Society

Bouteloup-Demange, Corinne; Claeyssens, Sophie; Maillot, Celine; Lavoinne, Alain; Lerebours, Eric; Dechelotte, Pierre

doi: N/Apmid: 10801259

Abstract In hypercatabolic patients, the beneficial effects of glutamine on gut mucosa could be partly due to a stimulation of protein synthesis. The fractional synthesis rate (FSR) of gut mucosal protein was measured in four groups of healthy volunteers treated with glucocorticoids for 2 days. Two groups were studied in the postabsorptive state while receiving glutamine or a nitrogen equivalent (control) and two groups in the fed state with or without glutamine, using a 5-h intravenous infusion of 13 Cleucine, 2 H 5 phenylalanine, and cortisone. After nutrient and tracer infusion, duodenal biopsies were taken. In the postabsorptive state, FSR of gut mucosal protein were 87 and 76%/day in the control group and 130% ( P = 0.058 vs. control) and 104% ( P = 0.17 vs. control)/day in the glutamine group, with leucine and phenylalanine as tracers, respectively. During feeding, FSR did not increase and no significant difference was observed between glutamine and control groups. Overall, FSR of the four groups were two- to threefold higher than those obtained previously in healthy humans, suggesting that glucocorticoids may increase gut mucosal protein synthesis. However, in this situation, a moderate enteral glutamine supply failed to demonstrate a significant effect on gut mucosal protein synthesis in the postabsorptive state and during feeding. stable isotopes duodenum hypercatabolic state fasted and fed states Footnotes Address for reprint requests and other correspondence: C. Bouteloup-Demange, Laboratoire de Nutrition Humaine, 58, rue Montalembert, BP 321, 63009 Clermont-Ferrand, Cedex 1, France. This study was supported by grants from the Ministère de la Santé (PHRC 94-084HP) and from the Fondation pour l'Association Charles Nicolle. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 2000 the American Physiological Society

Umar, Shahid; Sellin, Joseph H.; Morris, Andrew P.

doi: N/Apmid: 10801269

Abstract In the companion article (Umar S, Scott J, Sellin JH, Dubinsky WP, and Morris AP, Am J Physiol Gastrointest Liver Physiol 278: 753–764, 2000), we have shown that transmissible murine colonic hyperplasia (TMCH) increased cellular cystic fibrosis transmembrane conductance regulator (CFTR) mRNA and protein expression, relocalized CFTR within colonocytes, and enhanced mucosal cAMP-dependent Cl − secretion. We show here that these changes were dependent on elevated cellular levels of membrane-bound Ca 2+ - and diacylglycerol-sensitive protein kinase C (PKC) activity (12-fold), induced by selective (3- to 4-fold) rises in conventional PKC (cPKC) isoform expression and membrane translocation. Three cPKC isoforms were detected in isolated crypts: α, β1, and β2. cPKC-β1 rises preceded and those of cPKC-α and cPKC-β2 paralleled cellular hyperproliferation and its effects on CFTR expression and cAMP-dependent Cl − current secretion. Only cPKC-β1 and cPKC-β2 were membrane translocated during TMCH. Furthermore, only cPKC-β1 trafficked to the nucleus, whereas cPKC-β2 remained partitioned among cytosolic, membrane, and cytoskeletal subcellular fractions. Modest increases in novel PKC-ε (nPKC-ε) expression and subcellular membrane partitioning were recorded during TMCH, but no changes were seen for PKC-δ or -η. No nPKC isoform nuclear partitioning was detected. The orally bioactive cPKC inhibitor Ro-32–0432 reversed both TMCH and elevated cellular CFTR mRNA levels, whereas a pharmacologically inert analog (Ro-31–6045) failed to inhibit either response. On the basis of these facts, we present a new hypothesis whereby PKC-dependent cellular proliferation promotes endogenous cellular CFTR levels. PKC-β1 was identified as a candidate regulatory PKC isoform. protein kinase C cystic fibrosis transmembrane conductance regulator anion transport regulation mouse Footnotes Address for reprint requests and other correspondence: A. P. Morris, Dept. of Internal Medicine, Division of Gastroenterology, Hepatology, and Nutrition, The Univ. of Texas Health Science Center at Houston, Medical School, Houston, TX 77030 (E-mail: [email protected] ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 2000 the American Physiological Society

Vogiagis, Daphne; Glare, Eric M.; Misajon, Aileen; Brown, Wendy; O'Brien, Paul E.

doi: N/Apmid: 10801275

Abstract Prostaglandins play a critical role in gastric mucosal cytoprotection and decrease progressively with age. Cyclooxygenase (COX), the rate-limiting enzyme for prostaglandin synthesis, exists in two isoforms, COX-1 and COX-2. The rat COX-1 gene expresses an alternatively spliced mRNA COX-1 splice variant (SV) that may, at best, code for a truncated COX-1 protein. With the use of competitive PCR, we determined whether COX gene expression was altered in the stomach with increasing age and after gastric ulcer induction. COX-1 mRNA was significantly reduced in the aged, and COX-1SV mRNA was significantly higher in the adults compared with the young and aged stomach. Levels of COX-1 and COX-2 were similarly expressed in the normal stomach. In acute gastric ulcers, only COX-2 mRNA levels were significantly elevated. When ulcers were undergoing healing and repair, COX-1 and COX-2 mRNA levels were significantly elevated. Age-related changes in COX-1 and COX-1SV but not COX-2 mRNA may alter gastric mucosal cytoprotection. Furthermore, COX-1 and COX-2 may both contribute to the healing of a gastric ulcer. splice variant competitive PCR gene expression gastric ulcer ulcer healing Footnotes Address for reprint requests and other correspondence: D. Vogiagis, Dept. of Surgery, Monash Univ. Medical School, Alfred Hospital, Prahran, Victoria 3181, Australia. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 2000 the American Physiological Society

Santuré, Marta; Pitre, Maryse; Gaudreault, Nathalie; Marette, André; Nadeau, André; Bachelard, Hélène

doi: N/Apmid: 10801260

Abstract We investigated the long-term effect of metformin treatment on blood pressure, insulin sensitivity, and vascular responses to insulin in conscious spontaneously hypertensive rats (SHR). The rats were instrumented with intravascular catheters and pulsed Doppler flow probes to measure blood pressure, heart rate, and blood flow. Insulin sensitivity was assessed by the euglycemic hyperinsulinemic clamp technique. Two groups of SHR received metformin (100 or 300 mg ⋅ kg − 1 ⋅ day − 1 ) for 3 wk while another group of SHR and a group of Wistar Kyoto (WKY) rats were left untreated. We found that vasodilation of skeletal muscle and renal vasculatures by insulin is impaired in SHR. Moreover, a reduced insulin sensitivity was detected in vivo and in vitro in isolated soleus and extensor digitorum longus muscles from SHR compared with WKY rats. Three weeks of treatment with metformin improves the whole-body insulin-mediated glucose disposal in SHR but has no blood pressure-lowering effect and no influence on vascular responses to insulin (4 mU ⋅ kg − 1 ⋅ min − 1 ). An improvement in insulin-mediated glucose transport activity was detected in isolated muscles from metformin-treated SHR, but in the absence of insulin no changes in basal glucose transport activity were observed. It is suggested that part of the beneficial effect of metformin on insulin resistance results from a potentiation of the hormone-stimulating effect on glucose transport in peripheral tissues (mainly skeletal muscle). The results argue against a significant antihypertensive or vascular effect of metformin in SHR. insulin sensitivity hypertension blood flow skeletal muscle Footnotes Address for reprint requests and other correspondence: H. Bachelard, Hypertension Research Unit, Laval Univ. Hospital Research Center, 2705 Blvd. Laurier, Ste-Foy, Québec, Canada G1V 4G2 (E-mail: [email protected] ). This work was supported by grants from the Medical Research Council of Canada (H. Bachelard) and Lyonnaise Industrielle Pharmaceutique. H. Bachelard is a chercheur-boursier of the Heart and Stroke Foundation of Canada. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 2000 the American Physiological Society

Pizarro, Theresa T.; Arseneau, Kristen O.; Cominelli, Fabio

doi: N/Apmid: 10801257

Abstract Crohn's Disease (CD) affects more than 500,000 individuals in the United States and represents the second most common chronic inflammatory disorder after rheumatoid arthritis. Although major advances have been made in defining the basic mechanisms underlying chronic intestinal inflammation, the precise etiopathogenesis of CD remains unknown. We have recently characterized two novel mouse models of enteritis that express a CD-like phenotype, namely the TNF ΔARE model of tumor necrosis factor (TNF) overexpression and the SAMP1/Yit model of spontaneous ileitis. The unique feature of these models is that they closely resemble CD for location and histopathology. These genetically manipulated new models of intestinal inflammation offer a powerful tool to investigate potential causes of human disease and may allow the development of novel disease-modifying therapeutic modalities for the treatment of CD. ileitis cytokines inflammation Footnotes Address for reprint requests and other correspondence: F. Cominelli, Div. of Gastroenterology and Hepatology, Univ. of Virginia Health System, PO Box 800708, Charlottesville, VA 22908 (E-mail: [email protected] ). ↵ * Eleventh in a series of invited articles on Lessons From Genetically Engineered Animal Models. The studies described in this article were supported by National Institute of Diabetes and Digestive and Kidney Diseases Grants DK-42191, DK-55812, and DK-07769 to F. Cominelli. Copyright © 2000 the American Physiological Society

Jones, Brett E.; Lo, Chau R.; Liu, Hailing; Pradhan, Zehra; Garcia, Lydia; Srinivasan, Anu; Valentino, Karen L.; Czaja, Mark J.

doi: N/Apmid: 10801261

Abstract Reactive oxygen intermediates (ROI) have been implicated as mediators of hepatocyte death resulting from a variety of forms of liver injury. To delineate the mechanisms that underlie ROI-induced apoptosis, the roles of caspase activation and nuclear factor-κB (NF-κB) signaling were determined in the rat hepatocyte cell line RALA255-10G after treatment with H 2 O 2 or the superoxide generator menadione. By 8 h, H 2 O 2 and menadione caused 26% and 33% cell death, respectively. Death from both ROI occurred by apoptosis as indicated by morphology under fluorescence microscopy, the induction of caspase activation and DNA fragmentation, and the cleavage of poly(ADP-ribose) polymerase. Despite the presence of caspase activation in both forms of apoptosis, caspase inhibition blocked H 2 O 2 - but not menadione-induced apoptosis. In contrast, inhibition of NF-κB activation decreased cell death from both ROI. Different ROI, therefore, induce distinct apoptotic pathways in RALA hepatocytes that are both caspase dependent and independent. In contrast to the known protective effect of NF-κB activation in tumor necrosis factor-α-induced hepatocyte apoptosis, NF-κB promotes hepatocellular death from ROI in these cells. reactive oxygen intermediates liver menadione Footnotes Address for reprint requests and other correspondence: M. J. Czaja, Marion Bessin Liver Research Center, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461 (E-mail: [email protected] ). This study was supported by National Institute of Diabetes and Digestive and Kidney Diseases Grant DK-44234 (M. J. Czaja), an Australian National Health and Medical Council Research Scholarship (B. E. Jones), and an American Digestive Health Foundation Astra/Merck Fellowship/Faculty Transition Award (B. E. Jones). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 2000 the American Physiological Society

Umar, Shahid; Scott, Jason; Sellin, Joseph H.; Dubinsky, William P.; Morris, Andrew P.

doi: N/Apmid: 10801268

Abstract Fluid transport in the large intestine is mediated by the cystic fibrosis gene product and cAMP-dependent anion channel cystic fibrosis transmembrane conductance regulator (CFTR). cAMP-mediated Cl − secretion by gastrointestinal cell lines in vitro has been positively correlated with the insertion of CFTR into the apical membrane of differentiated senescent colonocytes and negatively correlated with the failure of CFTR to insert into the plasma membrane of their undifferentiated proliferating counterparts. In native tissues, this relationship remains unresolved. We demonstrate, in a transmissible murine colonic hyperplasia (TMCH) model, that (8-fold) colonocyte proliferation was accompanied by increased cellular CFTR mRNA and protein expression (8.3- and 2.4-fold, respectively) and enhanced mucosal cAMP-dependent Cl − secretion (2.3-fold). By immunofluorescence microscopy, cellular CFTR expression was restricted to the apical pole of cells at the base of the epithelial crypt. In contrast, increased cellular proliferation in vivo led to increases in both the cellular level and the total number of cells expressing this anion channel, with cellular CFTR staining extending into the crypt neck region. Hyperproliferating colonocytes accumulated large amounts of CFTR in apically oriented subcellular perinuclear compartments. This novel mode of CFTR regulation may explain why high endogenous levels of cellular CFTR mRNA and protein within the TMCH epithelium were not matched with larger increases in transmucosal CFTR Cl − current. cystic fibrosis transmembrane conductance regulator regulation location mRNA protein Footnotes Address for reprint requests and other correspondence: A. P. Morris, Dept. of Internal Medicine, Division of Gastroenterology, Hepatology and Nutrition, The Univ. of Texas Health Science Center at Houston, Medical School, Houston, Texas, 77030 (E-mail: [email protected] ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. §1734 solely to indicate this fact. Copyright © 2000 the American Physiological Society